Скачать презентацию Drops on patterned surfaces Halim Kusumaatmaja Alexandre Dupuis Скачать презентацию Drops on patterned surfaces Halim Kusumaatmaja Alexandre Dupuis

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Drops on patterned surfaces Halim Kusumaatmaja Alexandre Dupuis Julia Yeomans Drops on patterned surfaces Halim Kusumaatmaja Alexandre Dupuis Julia Yeomans

Summary The model Chemically patterned surfaces Spreading on stripes Hysteresis Superhydrophobic surfaces Introduction Hysteresis Summary The model Chemically patterned surfaces Spreading on stripes Hysteresis Superhydrophobic surfaces Introduction Hysteresis Transitions between states Dynamics

Equations Navier-Stokes equations of motion continuity Navier-Stokes No-slip boundary conditions on the velocity Equations Navier-Stokes equations of motion continuity Navier-Stokes No-slip boundary conditions on the velocity

Equilibrium free energy bulk term interface free energy surface term Van der Waals controls Equilibrium free energy bulk term interface free energy surface term Van der Waals controls surface tension controls contact angle

Controlling the contact angle Surface free energy Minimising the free energy leads to: Boundary Controlling the contact angle Surface free energy Minimising the free energy leads to: Boundary condition on the Euler-Lagrange equation A relation between the contact angle and the surface field

Summary The model Chemically patterned surfaces Spreading on stripes Hysteresis Superhydrophobic surfaces Introduction Hysteresis Summary The model Chemically patterned surfaces Spreading on stripes Hysteresis Superhydrophobic surfaces Introduction Hysteresis Transitions between states Dynamics

Chemically striped surfaces: drop spreading Chemically striped surfaces: drop spreading

Experiments (J. Léopoldès and D. Bucknall) 64 o / 5 o Experiments (J. Léopoldès and D. Bucknall) 64 o / 5 o

LB simulations on substrate 4 • Two final (meta-)stable state observed depending on the LB simulations on substrate 4 • Two final (meta-)stable state observed depending on the point of impact. • Dynamics of the drop formation traced. • Quantitative agreement with experiment. Simulation vs experiments Evolution of the contact line

Impact near the centre of the lyophobic stripe Impact near the centre of the lyophobic stripe

Impact near a lyophilic stripe Impact near a lyophilic stripe

LB simulations on substrate 4 • Two final (meta-)stable state observed depending on the LB simulations on substrate 4 • Two final (meta-)stable state observed depending on the point of impact. • Dynamics of the drop formation traced. • Quantitative agreement with experiment. Simulation vs experiments Evolution of the contact line

80 o /90 o 80 o /90 o

Two wide stripes: 110 o /130 o hydrophilic hydrophobic hydrophilic Two wide stripes: 110 o /130 o hydrophilic hydrophobic hydrophilic

80 o /90 o 80 o /90 o

Characteristic spreading velocity A. Wagner and A. Briant Characteristic spreading velocity A. Wagner and A. Briant

Summary The model Chemically patterned surfaces Spreading on stripes Hysteresis Superhydrophobic surfaces Introduction Hysteresis Summary The model Chemically patterned surfaces Spreading on stripes Hysteresis Superhydrophobic surfaces Introduction Hysteresis Transitions between states Dynamics

Hysteresis Hysteresis

Hysteresis Hysteresis

Hysteresis Hysteresis

Hysteresis Hysteresis

Hysteresis Hysteresis

Hysteresis Hysteresis

Hysteresis Hysteresis

Hysteresis Hysteresis

Hysteresis Hysteresis

Hysteresis slips at angle advancing Hysteresis slips at angle advancing

Hysteresis pinned until Hysteresis pinned until

Hysteresis pinned until Hysteresis pinned until

Hysteresis slips smoothly across hydrophobic stripe Hysteresis slips smoothly across hydrophobic stripe

Hysteresis slips smoothly across hydrophobic stripe Hysteresis slips smoothly across hydrophobic stripe

Hysteresis jumps back to Hysteresis jumps back to

Hysteresis advancing stick slip jump (slip) Hysteresis advancing stick slip jump (slip)

Hysteresis advancing stick slip jump (slip) receding stick (slip) jump slip Hysteresis advancing stick slip jump (slip) receding stick (slip) jump slip

(Hysteresis) loop a contact angle a volume advancing contact angle receding contact angle a (Hysteresis) loop a contact angle a volume advancing contact angle receding contact angle a

(Hysteresis) loop slip contact angle stick volume advancing contact angle receding contact angle jump (Hysteresis) loop slip contact angle stick volume advancing contact angle receding contact angle jump

Hysteresis: 3 dimensions A. squares 60 o background 110 o B. squares 110 o Hysteresis: 3 dimensions A. squares 60 o background 110 o B. squares 110 o background 60 o

Hysteresis: 3 dimensions A squares hydrophilic B squares hydrophobic Hysteresis: 3 dimensions A squares hydrophilic B squares hydrophobic

Hysteresis: 3 dimensions macroscopic contact angle versus volume A stick B jump Hysteresis: 3 dimensions macroscopic contact angle versus volume A stick B jump

Hysteresis: 3 dimensions macroscopic contact angle versus volume A B 94 o 92 o Hysteresis: 3 dimensions macroscopic contact angle versus volume A B 94 o 92 o 110/60

Hysteresis on chemically patterned surfaces 1. Slip, stick, jump behaviour, but jumps at different Hysteresis on chemically patterned surfaces 1. Slip, stick, jump behaviour, but jumps at different volumes in different directions (but can be correlated) 2. Contact angle hysteresis different in different directions 3. Advancing angle (92 o) bounded by qmax (110 o) Receding angle (80 o) bounded by qmin (60 o) 4. Free energy balance between surface / drop interactions and interface distortions determines the hysteresis

Summary The model Chemically patterned surfaces Spreading on stripes Hysteresis Superhydrophobic surfaces Introduction Hysteresis Summary The model Chemically patterned surfaces Spreading on stripes Hysteresis Superhydrophobic surfaces Introduction Hysteresis Transitions between states Dynamics

Superhydrophobic surfaces Superhydrophobic surfaces

Superhydrophobic surfaces Superhydrophobic surfaces

Two drop states suspended drop collapsed drop He et al. , Langmuir, 19, 4999, Two drop states suspended drop collapsed drop He et al. , Langmuir, 19, 4999, 2003

Suspended and collapsed drops Suspended, q~160 o Homogeneous substrate, qeq=110 o Collapsed, q~140 o Suspended and collapsed drops Suspended, q~160 o Homogeneous substrate, qeq=110 o Collapsed, q~140 o

Hysteresis: suspended state 180 o Hysteresis: suspended state 180 o

Hysteresis: suspended state advancing receding Suspended drop Advancing contact angle 180 o: pinned on Hysteresis: suspended state advancing receding Suspended drop Advancing contact angle 180 o: pinned on outside of posts Receding contact angle : pinned on outside of posts

Hysteresis: collapsed state receding Collapsed drop Advancing contact angle 180 o: pinned on outside Hysteresis: collapsed state receding Collapsed drop Advancing contact angle 180 o: pinned on outside of posts Receding contact angle -90 o: pinned on outside AND inside of posts

Hysteresis: three dimensions 2 D Suspended drop: advancing angle 180 o receding angle qe Hysteresis: three dimensions 2 D Suspended drop: advancing angle 180 o receding angle qe Collapsed drop: advancing angle 180 o receding angle qe-90 o 3 D

Hysteresis: three dimensions 2 D Suspended drop: advancing angle 180 o receding angle qe Hysteresis: three dimensions 2 D Suspended drop: advancing angle 180 o receding angle qe 3 D 180 o > qe Free energy barrier very small Collapsed drop: advancing angle 180 o receding angle qe-90 o ~180 o > qe-90 o

Hysteresis on superhydrophobic surfaces 1. Advancing contact angles are close to 180 o 2. Hysteresis on superhydrophobic surfaces 1. Advancing contact angles are close to 180 o 2. Hysteresis smaller for suspended than collapsed drop High receding contact angle -- weak adhesion Small contact angle hysteresis – slides easily? ? 3. Free energy balance between drop -- surface interactions and interface distortion determines the hysteresis ? ? Forced hysteresis ? ? Changing relative length scales ? ? Relation between hysteresis and easy run off

Summary The model Chemically patterned surfaces Spreading on stripes Hysteresis Superhydrophobic surfaces Introduction Hysteresis Summary The model Chemically patterned surfaces Spreading on stripes Hysteresis Superhydrophobic surfaces Introduction Hysteresis Transitions between states Dynamics

Drop collapse: Mathilde Reyssat and David Quere 200 m Drop collapse: Mathilde Reyssat and David Quere 200 m

Drop collapse: simulations Drop collapse: simulations

1. Curvature driven collapse : short posts 2. Free energy driven collapse : long 1. Curvature driven collapse : short posts 2. Free energy driven collapse : long posts

Drop collapse: short posts Drop collapse: short posts

Drop collapse: short posts Drop collapse: short posts

Drop collapse: short posts Drop collapse: simulations Mathilde Reyssat and David Quere Drop collapse: short posts Drop collapse: simulations Mathilde Reyssat and David Quere

Drop collapse: shallow posts Drop collapse: shallow posts

Drop collapse: long posts Drop collapse: long posts

Drop collapse: long posts qe Deep posts: contact angle reaches qe on side of Drop collapse: long posts qe Deep posts: contact angle reaches qe on side of posts

Variation of free energy with post height q>qe q<qe Variation of free energy with post height q>qe q

Drop collapse: two dimensions Drop collapse: two dimensions

Drop position with decreasing contact angle Drop position with decreasing contact angle

Collapse on superhydrophobic surfaces Shallow posts: curvature driven collapse Deep posts: 2 dimensions – Collapse on superhydrophobic surfaces Shallow posts: curvature driven collapse Deep posts: 2 dimensions – free energy driven collapse Deep posts: 3 dimensions – is collapse possible ? ?

Summary The model Chemically patterned surfaces Spreading on stripes Hysteresis Superhydrophobic surfaces Introduction Hysteresis Summary The model Chemically patterned surfaces Spreading on stripes Hysteresis Superhydrophobic surfaces Introduction Hysteresis Transitions between states Dynamics

With thanks to Alexandre Dupuis Halim Kusumaatmaja With thanks to Alexandre Dupuis Halim Kusumaatmaja

Drop velocity: suspended drop Droplet velocity Drop velocity Drop velocity: suspended drop Droplet velocity Drop velocity

Drop velocity: collapsed drop Dynamics of collapsed droplets Drop velocity Drop velocity: collapsed drop Dynamics of collapsed droplets Drop velocity

Summary The model Chemically patterned surfaces Spreading on stripes Hysteresis Superhydrophobic surfaces Introduction Hysteresis Summary The model Chemically patterned surfaces Spreading on stripes Hysteresis Superhydrophobic surfaces Introduction Hysteresis Transitions between states Dynamics

With thanks to Alexandre Dupuis Halim Kusumaatmaja With thanks to Alexandre Dupuis Halim Kusumaatmaja

Chemically striped surfaces: drop motion Chemically striped surfaces: drop motion

Two wide stripes: 110 o /130 o hydrophilic hydrophobic hydrophilic Two wide stripes: 110 o /130 o hydrophilic hydrophobic hydrophilic

80 o /90 o 80 o /90 o

60 o /110 o 60 o /110 o

Base radius as a function of time Base radius as a function of time

Controlling the contact angle Surface free energy Minimising the free energy leads to: Boundary Controlling the contact angle Surface free energy Minimising the free energy leads to: Boundary condition on the Euler-Lagrange equation A relation between the contact angle and the surface field

Mathilde Callies and David Quere 2006 Mathilde Callies and David Quere 2006